Bump version to 3.8.1

Author: sgravrock

lib/jasmine/version.rb

@@ -1,3 +1,3 @@
 module Jasmine
-  VERSION = "3.8.0"
+  VERSION = "3.8.1"
 end

release_notes/3.8.1.md

@@ -0,0 +1,19 @@
+# Jasmine Gem 3.8.1 Release Notes
+
+This release updates the Rack dependency to >= 2.1.4 due to security 
+vulnerabilities in earlier versions of Rack. There are no other changes.
+
+## Supported Environments
+
+The Jasmine gem has been tested in the following environments:
+
+| Rails version   | Ruby versions |
+|-----------------|---------------|
+| 6               | 2.5-3.0       |
+| 5               | 2.3-2.7       |
+| 4               | 2.3-2.6       |
+| Non-Rails usage | 2.3-3.0       |
+
+See the
+[jasmine-core release notes](https://github.com/jasmine/jasmine/blob/main/release_notes/3.8.0.md)
+for supported browsers.